As a result of a recent increase in human population, the demand for food is projected to rise more than 70% in 2050 (FAO, 2009), and twice as much livestock products, that is, meat and dairy products, are projected to be produced in order to meet the demand. However, the livestock industry, especially the ruminant animal industry, has recently been recognized to have a negative impact on the regional and global environment. An intensive livestock industry contributes to air, soil, water, and other environmental pollution regionally, and is known as a major causal factor of greenhouse gases in terms of the global environment. In particular, Livestock's Long Shadow (Steinfeld et al., 2006) released by the FAO in 2006, specifically reported the impact of the livestock industry on the environment.
The amount of annual greenhouse gas emissions generated in the livestock industry is predicted to be about 4.1 to 7.1 billion tons of CO2 equivalents, which is equivalent to about 15% to 24% of total greenhouse gas emissions (Steinfeld et al., 2006). The amounts of carbon dioxide, methane, and nitrous oxide generated by livestock account for 9%, 35% to 40%, and 65%, respectively, of the total emissions generated by human-related activities, thereby reaching a serious level.
As is known, most methane and nitrous oxide are generated from farming livestock. The feed consumed by ruminant animals is decomposed into volatile fatty acids, hydrogen, carbon dioxide, and ammonia nitrogen by fermentation of anaerobic microorganisms (bacteria, protozoa, and fungi) in the ruminant stomach, and the hydrogen and carbon dioxide are converted to methane by methanogenic bacteria. The methane is then released into the atmosphere, and not absorbed into the body. A recent study conducted by a research team in New Zealand has shown that 80% of greenhouse gases are from farms, only 3% are from meat processing after slaughter, 5% are from meat transportation, and lastly, 12% are from the phase of consumption by consumers (Ledgard et al., 2010). Additionally, feed energy is lost (2% to 15%) when nutrients are converted into methane in a gaseous form. Accordingly, research for reducing methane production in the ruminant stomach of the ruminant animals has been continuously conducted to enhance productivity of livestock and reduce greenhouse gases which are harmful to the environment.
Currently, as a method for reducing methane gas production of ruminant animals, addition of an antibiotic such as monensin into the feed, elimination of protozoa in the ruminant stomach, addition of a halogen compound into the feed, or feeding of probiotics has been studied.
However, the addition of the antibiotic to the feed to inhibit the methane production is considered to be inappropriate, as the global trend is to restrict use of chemicals or antibiotics as feed additives, and residue thereof may be harmful to the human body. The elimination of protozoa may lead to a reduction of a cellulose level, and the addition of halogen compounds to the feed may lead to a discontinuation of methane gas inhibition, as well as safety issues such as halogen accumulation in the livestock. Further, the feeding of probiotics may have problem with inconsistency in probiotic fermentations and strains added during every experiment of methane gas production.
Meanwhile, Korean Patent Application Publication No. 10-2006-0019062 discloses a feed composition for inhibiting methane production of ruminant animals. The patent has a technical feature in that methane gas production of the ruminant animals is reduced by feeding the ruminant animals the feed composition comprising at least one selected from the group consisting of ginger, chive extracts, and conjugated linoleic acids. However, as the feed composition comprising the ginger, chive extracts, and conjugated linoleic acids requires an additional preparation process, the feed composition is not readily available. Also, the feed composition has problem with increase of purchase costs due to high preparation costs.
Therefore, a technique for efficiently reducing methane gas which is harmful to the environment, while minimizing the negative impact on livestock productivity is needed.